Digimap is an online map and data delivery service which offers a number of data collections, including Ordnance Survey, historical, geological, LiDAR and marine maps and spatial data.
You can create or interrogate a map online by selecting an appropriate base map, adding annotations and customising the content, and use measurement and query tools to learn more about a study area. It is also possible to download the raw spatial data in a wide range of formats for use in GIS, CAD or image processing software.
So long as your institution subscribes (and over 166 universities do), users simply need to register for an individual account and then they get instant access to data for online mapping or to download. There is a very good helpdesk should you need it at firstname.lastname@example.org.
OS Open Data is a source of more generalised data, often at a smaller scale. It is available under the Open Government Licence so all forms or onward use are permissible as long as the origin of the data is acknowledged.
Don’t forget to always acknowledge the copyright and source of your data.